Apparatus and methods for capacitively coupled plasma vapor processing of semiconductor wafers

ABSTRACT

A capacitively coupled plasma reactor comprising a processing chamber, a first electrode, a second electrode and a thermoelectric unit. The processing chamber has an upper portion with a gas inlet and a lower portion, and the upper portion is in fluid communication with the lower portion. The first electrode has a front side and a backside and is positioned at the upper portion of the processing chamber. The second electrode is positioned in the lower portion of the processing chamber and is spaced apart from the front side of the first electrode. The thermoelectric unit is positioned proximate to the backside of the first electrode and is capable of heating and cooling the first electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No. 11/688,144filed Mar. 19, 2007, now U.S. Pat. No. 8,375,890, which is incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to processing semiconductor wafers in acapacitively coupled plasma reaction chamber.

BACKGROUND

Thin film deposition and etching techniques are used in semiconductorwafer processing to build interconnects, plugs, gates, capacitors,transistors or other microfeatures. Thin film deposition and etchingtechniques are continually improving to meet the ever increasing demandsof the industry as the sizes of microfeatures decrease and the number ofmicrofeatures increases. As a result, the density of the microfeaturesand aspect ratios of depressions (e.g., the ratio of the depth to thesize of the opening) are increasing. Thin film techniques accordinglystrive to consistently produce highly accurate processing results. Manyetching and deposition processes, for example, seek to form uniformlayers or other layers that uniformly cover sidewalls, bottoms andcorners in deep depressions that have very small openings.

CCP processes are often challenging because the characteristics of theplasma generated in the reaction chamber as well as the deposition oretching results depend on the electrode temperature, but it is difficultto quickly control the temperature of the first or upper electrodewithin a small range. For example, in conventional CCP chambers athermal control unit controls the first electrode temperature, howevertypical thermal control units have large time constants and do notaccurately maintain a set or constant temperature due to heat changesduring processing (e.g., when the electrodes are biased on and off toform the plasma). Another problem associated with thermal control of thefirst electrode is that inconsistent electrode temperatures can produceinconsistent processing results. For example, with a fluorocarbonplasma, the amount of fluorocarbon polymer that is attracted to thefirst electrode, and therefore away from the wafer, is inverselyproportional to the temperature of the first electrode. Conventional CCPchambers, however, have separate heating and cooling elements thatincrease the thermal impedance of the upper portion 4. Accordingly,conventional CCP reactors are subject to inconsistent startingtemperatures and thermal fluctuations of the first electrode duringplasma generation that can result in variability in the processingresults.

Another problem associated with the thermal control of the firstelectrode is differential thermal expansion between hardware proximateto the upper electrode. The different components of the upper portionhave different coefficients of thermal expansion, which can causerubbing and stress during temperature cycling. This rubbing may produceparticles that are conveyed by the process gas stream to thesemiconductor wafer forming defects on the semiconductor wafer. Suchnon-uniformities and defects limit the utility of CCP vapor processingfor forming very small microfeatures. Accordingly, a need exists forimproved thermal control of the electrode and thermal management of theupper portion for consistent processing results in a CCP reactor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a plasma etch ordeposition processing system in accordance with the prior art.

FIG. 2 is a schematic cross-sectional view of a plasma etch ordeposition processing system in accordance with an embodiment of theinvention.

FIGS. 3A, 3B, and 3C are schematic cross-sectional views of plasma etchor deposition processing systems in accordance with embodiments of theinvention.

FIG. 4A is a schematic top plan view and FIG. 4B is a schematiccross-sectional view of an electrode and thermoelectric unit inaccordance with an embodiment of the invention.

FIG. 5 is a schematic top plan view of an electrode and thermoelectricunit in accordance with an embodiment of the invention.

FIGS. 6A and 6B are schematic cross-sectional views of an electrode andthermoelectric unit in accordance with embodiments of the invention.

FIGS. 7A and 7B are flow diagrams of processes in accordance with aembodiments of the invention.

DETAILED DESCRIPTION

Several embodiments of the present invention are directed towardsemiconductor wafer processing systems and methods for depositing oretching materials on semiconductor wafers. Many specific details of theinvention are described below with reference to systems for depositingor etching materials on semiconductor wafers with capacitively coupledplasma (CCP) in chemical vapor processes. The term “semiconductor wafer”is used throughout to include substrates upon which and/or in whichmicroelectronic devices, micromechanical devices, data storage elements,read/write components and other features are fabricated. For example,semiconductor wafers can be silicon or gallium arsenide wafers, glasssubstrates, insulative substrates and substrates made from many othertypes of materials. The semiconductor wafers typically have submicronfeatures and components with dimensions of a few nanometers or greater.Furthermore, the term “gas” is used throughout to include any form ofmatter that has no fixed shape and will conform in volume to the spaceavailable, which specifically includes vapors (i.e., a gas having atemperature less than the critical temperature so that it may beliquefied or solidified by compression at a constant temperature).Several embodiments in accordance with the invention are set forth inFIGS. 2-7B and the following text to provide a thorough understanding ofparticular embodiments of the invention. Moreover, several otherembodiments of the invention can have different configurations,components or procedures than those described in this section. A personskilled in the art will understand, therefore, that the invention mayhave additional embodiments, or that the invention may be practicedwithout several details of the embodiments shown in FIGS. 2-7B.

FIG. 2 is a schematic cross-sectional view of a plasma vapor processingsystem 200 for depositing or etching material on a semiconductor waferW. In this embodiment, the processing system 200 includes a reactor 210having an upper portion 212 and a lower portion 214. The upper portion212 includes a gas inlet 218, and gases can flow from the upper portion212 to the lower portion 214. The lower portion 214 includes aprocessing chamber 216. The processing chamber 216 can be a low pressurechamber capable of producing and sustaining a low pressure environment.For example, the processing chamber 216 can be coupled to a vacuum pump(not shown) to reduce and maintain the pressure in the processingchamber 216. The reactor 210 further includes a first electrode 220 atthe upper portion 212 and a second electrode 230 in the lower portion214. The first electrode 220 has a front side 222 facing the processingchamber and a backside 224 opposite the front side 222. The secondelectrode 230 is spaced apart from the front side 222 of the firstelectrode 220. The first and second electrodes 220 and 230 are connectedto an RF power supply 215 and a ground, such that in operation one ofthe first or second electrodes 220 or 230 is biased by the RF powersupply 215 while the other electrode is grounded. In other embodiments,both of the first and second electrodes 220 and 230 are biased by the RFpower supply and a sidewall of the chamber 216 is grounded. The reactor210 further includes a thermoelectric unit 240 positioned at leastproximate to the backside 224 of the first electrode 220 and configuredto heat and/or cool the first electrode 220 during one or moreprocessing procedures.

The upper portion 212 includes an antechamber 213 for receiving a smallvolume of one or more process gases via the gas inlet 218. The gases,for example, can flow into the antechamber 213 at a constant pressurefor equal mixing to provide an even flow from the upper portion 212 tothe lower portion 214. The first electrode 220 includes one or morechannels or outlets 226 through which the gases flow from the upperportion 212 to the lower portion 214. In one embodiment, the firstelectrode 220 functions as a gas distributor between the upper portion212 and the lower portion 214. For example, the outlets 226 in the firstelectrode 220 can be sized and arranged to distribute the one or moreprocess gases into the lower portion 214. The outlets 226 can begenerally arranged relative to a wafer W positioned in the processingchamber 216 to provide a controlled distribution of the one or moreprocess gases onto the wafer W.

In certain embodiments, a gas inlet 219 can introduce the one or moreprocess gases into the first electrode 220. For example, as shown bybroken lines in FIG. 2, the first electrode 220 can include an innerchamber 228 and the gas inlet 219 can introduce the one or more processgases directly into the inner chamber 228 of the first electrode 220instead of the antechamber 213 in the upper portion 212. The one or moreprocess gases can accordingly flow through the first electrode 220 andinto the processing chamber 216 of the lower portion 214.

The thermoelectric unit 240 includes a first surface 242 and a secondsurface 244 opposite the first surface 242. The first surface 242 of thethermoelectric unit 220 is positioned proximate to the backside 224 ofthe first electrode 220. In specific embodiments, the thermoelectricunit 240 heats and/or cools the first electrode 220 by directconduction. For example, the first surface 242 of the thermoelectricunit can directly contact the backside 224 of the first electrode 220 todirectly conduct heat away from or to the first electrode 220. Thethermoelectric unit 240 may also include one or more ports or outlets246 to allow the one or more process gases to pass through thethermoelectric unit 240 and out of the upper portion 212. For example,the thermoelectric unit 240 can include a larger or smaller number ofoutlets 246, or the same number of outlets 246 as the number of outlets226 of the first electrode 220. In some embodiments, a pattern of theoutlets 246 of the thermoelectric unit 240 may coincide or match apattern of the outlets 226 of the first electrode 220. Alternatively,the pattern of the outlets 246 may differ from the pattern of theoutlets 226 of the first electrode 220, according to the deposition oretching needs of the process.

The thermoelectric unit 240 can be a Peltier heating and cooling unit.For example, when the thermoelectric unit 240 is connected to a voltagesource the first surface 242 of the thermoelectric unit 240 absorbs heatwhile the second surface 244 of the thermoelectric unit 240 emits heat.If the polarity of the voltage is reversed, the first surface 242 of thethermoelectric unit 240 emits heat while the second surface 244 of thethermoelectric unit 240 absorbs heat. Accordingly, the thermoelectricunit 240 provides heating and cooling at the same location and canrapidly switch between heating and cooling modes.

In the embodiment shown in FIG. 2, the upper portion also has a thermalcontrol unit or plate 250 enclosing the antechamber 213. The secondsurface 244 of the thermoelectric unit 240 is positioned proximate tothe plate 250. The second surface 244 is generally spaced apart from theplate 250 to provide space for the antechamber 213, but portions of theplate 250 and the second surface 244 may contact each other for betterheat transfer. However in some embodiments, the plate 250 contacts theentire second surface 244. The plate 250 includes a plurality ofchannels 252 for flowing a cooling or heating medium through the plate250 to cool or heat the thermoelectric unit 240 and the upper portion212. For example, water can flow through the plate 250 to add heat orremove heat from the second surface 244 of the thermoelectric unit 240depending on the relative temperatures of the thermoelectric unit 240and the plate 250. The water can be heated or cooled before flowingthrough the plate 250, or the water can be maintained approximately atroom temperature (e.g., 18-27° C.) before and/or while flowing throughthe plate 250.

The processing system can further include a gas supply 260 having one ormore process gases and a controller 264 operatively coupled to the gassupply 260. The gas supply 260 can include a one or more process gasesPG₁, PG₂, . . . , PG_(n) suitable for processing a semiconductor waferW. The gas supply 260 flows the one or more process gases PG₁, PG₂, . .. , PG_(n) through the gas inlet 218 into the upper portion 212, or inalternative embodiments through the gas inlet 219 into the firstelectrode 220. Accordingly, the reactor 210 can receive one or moreprocess gases that are selectively delivered to the upper portion 212 orthe first electrode 220 according to computer operable instructionscontained in the controller 264.

The lower portion 214 of the reactor 210 includes a wafer holder 217positioned in the processing chamber 216 at least proximate to thesecond electrode 230. The wafer holder 217 can be a component of thesecond electrode 230, or the wafer holder 217 can be a separatenonconductive component. The wafer holder 217 can also be a heated chuckor other device that holds the workpiece W during the processing.

The plasma vapor processing system 200 can provide rapid, accurate andconsistent thermal control of the first electrode 220 duringsemiconductor wafer processing. In operation, the first electrode 220and the second electrode 230 create an energy field to ionize the one ormore process gases and form a plasma in the processing chamber 216 ofthe lower portion 214. To begin processing, the thermoelectric unit 240heats the first electrode 220 to a desired starting temperature. Forexample, the starting temperature of the first electrode 220 may beapproximately 170° C. in a specific application. When the firstelectrode reaches the desired starting temperature, the controller 264flows one or more process gases into the upper portion 212 of thereactor 210. As the one or more process gases flow from the upperportion 212 to the processing chamber 216 of the lower portion 214, oneof the first or second electrodes 220 or 230 is biased with the RF powersupply 215 while the other electrode is grounded. Alternatively, both ofthe first and second electrodes are biased by the RF power supply 215while a sidewall of the chamber 216 is grounded. The first and secondelectrodes 220 and 230 create an energy field that ionizes the one ormore process gases to form the plasma in the processing chamber 216. Theplasma generated in the reactor 210 affects the temperature of the firstelectrode 220. For example, the plasma generation portion of aprocessing cycle can increase the temperature of the first electrode bya significant amount (e.g., about 20° C.). To counteract the heatgenerated by the plasma, the thermoelectric unit 240 can be used to coolthe first electrode 220 during this portion of the process to reduce thetemperature increase of the first electrode 220. Moreover, inembodiments where the thermoelectric unit 240 is a Peltier heating andcooling unit, the thermoelectric unit 240 can rapidly respond to heat orcool the first electrode 220 to maintain a generally constanttemperature. After completing the process, the electrodes 220 and 230are de-energized and the gas flow is stopped. The first electrode 220will then begin to cool and the thermoelectric unit 240 can be activatedto heat the first electrode 220 when the temperature falls below thedesired level.

Several embodiments of the reactor 210 can provide good control of thefirst electrode temperature because the thermoelectric unit 240 can bothheat or cool at the backside of the first electrode. More specifically,depending on the polarity of the voltage applied to the thermoelectricunit 240, the first surface 242 positioned proximate to the backside 224of the first electrode 220 will either heat or cool the first electrode220. When the first surface 242 heats the first electrode 220, thesecond surface 244 of the thermoelectric unit 240 will cool the upperportion 212 of the reactor 210. Accordingly, heat can be added to thesecond surface 244 to maintain thermal control and prevent excessivecooling of the hardware of the upper portion 212. For example, when thefirst surface 242 is heating the first electrode 220 and the secondsurface 244 is cooling the upper portion 212, the second surface 244 maycause condensation in the upper portion 212 if a sufficient amount ofheat is not added to the second surface 244. Alternatively, when thefirst surface 242 is cooling the first electrode 220, the second surface244 of the thermoelectric unit 240 will heat the upper portion 212.Accordingly, heat can be removed from the second surface 244 to maintainthermal control and prevent excessive heating or expansion of thehardware in the upper portion 212. The plate 250 positioned proximate tothe second surface 244 of the thermoelectric unit 240 can act as a heatsource or sink to the second surface 244. For example, flowing waterthrough the channels 252 of the plate 250 can provide sufficient thermalcontrol of the back surface 244 of the thermoelectric unit 240 to atleast partially avoid the problems associated with excessive cooling orheating of the upper portion 212. As a result, the primary heating andcooling of the first electrode 220 can both be performed at or near thefirst electrode 220. Several embodiments can accordingly provide rapidand accurate control of the first electrode temperature.

Positioning the thermoelectric unit 240 proximate to the first electrode220 in the upper portion 212 can further provide accurate and consistentthermal control of the first electrode 220 and improved thermalmanagement of the upper portion 212. For example, the first surface 242of the thermoelectric unit 240 can rapidly switch between heating andcooling modes by changing the polarity of the voltage applied to thethermoelectric unit 240. This rapid and dynamic control of thethermoelectric unit 240 increases the accuracy and consistency of thetemperature of the first electrode 220 before and during semiconductorwafer processing. Accordingly, the improved thermal control of the firstelectrode 220 can improve the characteristics of the plasma and theprocessing results on the wafer W.

In addition, positioning the thermoelectric unit 240 proximate to or incontact with the first electrode 220 can improve the thermalconductivity between the first electrode 220 and the thermoelectric unit240 for both heating and cooling modes. An improved thermal conductivitycan produce a reduced temperature gradient across the upper portion 212for a constant amount of transferred heat. For example, according toFourier's law, Q=−k_(eff)×∇T, where Q is the rate of heat transfer, k isthe lumped average thermal conductivity of the materials of the system,and ∇T is the temperature gradient, for a constant rate of heat transferQ, the thermal conductivity k is inversely proportional to thetemperature gradient ∇T. Accordingly, improving the thermal conductivityto transfer heat to or away from the backside 224 of the first electrode220 by positioning the thermoelectric unit 240 proximate to or incontact with the first electrode 220 can create a reduced temperaturegradient across the hardware of the upper portion 212, whiletransferring the same amount of heat from the upper portion 212.

The reduced temperature gradient across the upper portion 212 can alsodecrease the differential thermal expansion (DTE) of the differentmaterials in the upper portion 212. With reduced DTE, the hardwareproximate to the first electrode 220 will expand and contract lessresulting in less rubbing and stressing. This may reduce the number ofparticles generated at or near the first electrode 220. Accordingly, thereduced DTE can decrease the number of particles deposited on the waferW which in turn can reduce the number of defects on the wafer W duringprocessing.

In addition, the thermoelectric unit 240 can provide simplified thermalcontrol of the upper portion 212 while maintaining accurate andconsistent thermal control of the first electrode 220. As noted above,while the first surface 242 of the thermoelectric unit heats the firstelectrode 220, the second surface 244 cools the upper portion 212, andvice versa. The first surface 242 dominates the heat transfer at thefirst electrode 220. The thermal control of the second surface 244 canaccordingly be relaxed because of the large range of allowabletemperature differential between the first and second surfaces 242 and244. For example, the first surface 242 of the thermoelectric unit 240can be at a fixed temperature proximate to the backside 224 of the firstelectrode 220 while the temperature of the second surface 244 can varybecause the second surface 244 is spaced apart from the backside 224 ofthe first electrode 220. In a specific embodiment, the fixed temperatureat the first surface 242 can be 100° C. and the second surface can varybetween temperatures of 20° C. to 180° C. In additional embodiments,multiple thermoelectric units 240 can be stacked to provide amulti-stage thermoelectric unit, which is capable of providing atemperature difference of approximately 120° C. between the first andsecond surfaces of the stacked thermoelectric unit. Accordingly, thethermoelectric unit can create an allowable temperature range betweenthe first surface 242 and the second surface 244, while stillmaintaining accurate thermal control of the first surface 242 positionedproximate to or contacting the backside 224 of the first electrode 220.Therefore, cooling or heating water flowing through the plate 250 can bea heat sink or source to the second surface 244 of the thermoelectricunit 240. For example, a flow of room temperature water will likelysuffice to both heat and cool the second surface 244 of thethermoelectric unit 240 as the second surface 244 may not require stricttemperature control. Using room temperature water as the cooling and/orheating fluid in the plate 250 can considerably simplify the deign ofthe upper portion 212 of the reactor 210. As a result, severalembodiments of the reactor 210 can simplify the thermal control of theupper portion 212.

FIGS. 3A-C are schematic cross-sectional views of embodiments of plasmavapor processing systems 200 a-c. Like reference numbers refer to likecomponents in FIGS. 2, and 3A-C, and thus the description of suchcomponents will not be repeated with reference to the processing systems200 a-c. The difference between the processing system 200 shown in FIG.2 and the processing system 200 a shown in FIG. 3A is that theprocessing system 200 a has an upper portion 312 having a gasdistributor 370 positioned between a first electrode 320 and athermoelectric unit 340. The gas distributor 370 has a front side 372and a backside 374. The front side 372 of the gas distributor 370 ispositioned proximate to a backside 324 of the first electrode 320, andthe backside 374 of the gas distributor is positioned proximate to afirst surface 342 of the thermoelectric unit 340. In this embodiment,the thermoelectric unit 340 heats or cools the gas distributor 370 andfirst electrode 320 by conduction. For example, the first surface 342 ofthe thermoelectric unit 340 can directly contact the backside 374 of thegas distributor 370 and the front side 372 of the gas distributor 370can directly contact the backside 324 of the first electrode. In otherembodiments, the thermoelectric unit 340 can be spaced apart from thegas distributor 370 by a small gap.

The gas distributor 370 includes one or more channels or outlets 376through which gas can flow from the upper portion 312 to the lowerportion 214. For example, the outlets 376 can be sized and arranged toprovide desired processing results on the wafer W positioned on thewafer holder 217 in the lower portion 214. In addition, the gasdistributor 370 may include one or more chambers or plenums within thegas distributor 370. In certain embodiments, the thermoelectric unit 340may include one or more channels or outlets 346, and the first electrode320 may also include one or more channels or outlets 326 through whichone or more process gasses can flow. The thermoelectric unit 340 and thefirst electrode 320 can include a larger, smaller or the same number ofoutlets 346 and 326 as the number of outlets 376 of the distributor 370.A pattern of the outlets 346 and 326 may coincide or match a pattern ofthe outlets 376, or these patterns may differ according to theprocessing needs. The processing system 200 a can provide similarperformance characteristics as the processing system 200 shown in FIG.2.

Referring to FIG. 3B, the difference between the processing system 200 ashown in FIG. 3A and the processing system 200 b shown in FIG. 3B isthat the thermoelectric unit 340 is positioned between the firstelectrode 320 and the gas distributor 370. For example, the firstsurface 342 of the thermoelectric unit 340 is positioned proximate tothe backside 324 of the first electrode 320, and the second surface 344of the thermoelectric unit 340 is positioned proximate to the front side372 of the gas distributor 370. In the embodiment shown in FIG. 3B, thethermoelectric unit 340 is spaced apart from both the first electrode320 and the gas distributor 370. In other embodiments, however, thethermoelectric unit 340 can directly contact one or both of the firstelectrode 320 and the gas distributor 370. The outlets 326, 346 and 376are similar to the outlets described with reference to FIG. 3A, and theprocessing system can provide similar performance characteristics as theprocessing system 200 shown in FIG. 2 and the processing system 200 ashown in FIG. 3A.

Referring to FIG. 3C, the difference between the processing system 200 ashown in FIG. 3A and the processing system 200 c shown in FIG. 3C isthat a thermo control unit or plate 350 is positioned in contact withthe thermoelectric unit 340. The plate 350 includes a first surface 354that contacts the second surface 344 of the thermoelectric unit 340. Theplate 350 also includes a plurality of channels 352, similar to thechannels 252 described above, for flowing a cooling or heating mediumthrough the plate 350 to cool or heat the thermoelectric unit 340 andthe upper portion 312. The plate 350 also includes a plurality ofoutlets 356 similar to the outlets described above. The illustratedembodiment of FIG. 3C improves contact between the thermoelectric unit340 and the thermo control unit or plate 350, thus improving conductionand heat transfer in the upper portion 312.

FIG. 4A is a schematic top plan view and FIG. 4B is a schematiccross-sectional view of another embodiment of an electrode 420 and athermoelectric unit 440. In this embodiment, the thermoelectric unit 440comprises a plurality of individual independently operablethermoelectric elements 442 a, 442 b, . . . 442 n positioned at leastproximate to the first electrode 420. The illustrated embodiment of FIG.4A has concentric thermoelectric elements 442 a-n on the electrode 420.The electrode 420 and thermoelectric unit 440 can also include one ormore channels or outlets as described above. The thermoelectric elements442 a-n can differ in width outwardly from the center of the electrode420 according to different heating needs across the electrode 420. Eachthermoelectric element 442 a-n, for example, can be an independentlyoperable Peltier device to control the temperature of different regionsof the electrode 420 independently. The concentric configuration and theindependent operation of the thermoelectric elements 442 a-n can provideaccurate temperature control of the electrode 420 to better control thedeposition or etching process. For example, different factors may causean uneven temperature distribution across the electrode duringprocessing. These factors may include non-uniformities in the electrodematerial causing the temperature to vary across the electrode 420. Inaddition, non-uniform RF coupling of the electrode 420 can vary thetemperature in different areas or zones of the electrode 420. Forexample, non-uniform RF coupling at the periphery of the electrode 420can make the electrode hotter at the periphery such that depositionand/or etching rate at the edge of the wafer is different than at thecenter of the wafer. Furthermore, desired processing results may requiredifferent temperatures in different zones of the electrode 420. Forexample, a shaped profile deposition or etch layer may be preferableover a uniform layer. In specific embodiments, such as a seed layer forelectroplating or forming layers for chemical mechanical polishing, adome shaped profile that is thicker at the center compared to theperiphery may be desired. Accordingly, the thermoelectric elements 442a-n can be operated independently of each other to dynamicallycompensate for undesired temperature differences across the electrode420 or to achieve desired processing results by heating or coolingdifferent zones of the electrode 420 during a process cycle.

FIG. 5 is a schematic top plan view illustrating another embodiment ofan electrode 520 and thermoelectric unit 540. In this embodiment, thethermoelectric unit 540 has one or more thermoelectric elements 542 a,542 b, . . . , 542 n. The thermoelectric elements 542 a-n can bearranged in a grid-like pattern with respect to the electrode 520, orany other pattern for improving the thermal control of the electrode520. Accordingly, the thermoelectric elements 542 a-n can differ insize, shape and arrangement across the electrode 520. The configurationof the thermoelectric unit 540 of FIG. 5 can provide similar performancecharacteristics as the configuration shown in FIGS. 4A and 4B.

FIG. 6A is a schematic cross-sectional view of an additional embodimentof an electrode 620 and a thermoelectric unit 640. In this embodiment,the thermoelectric unit 640 is embedded or positioned within the firstelectrode 620. The first electrode 620 has a front portion 623 with afront side 622, and a back portion 625 with a backside 624. Thethermoelectric unit 640 is positioned between the first portion 623 andthe second portion 625 of the first electrode 620. The first electrode620 may have one or more channels or outlets 626, and the thermoelectricunit 640 may also have one or more channels or outlets 646 similar tothe outlets 226 and 246 described above. The thermoelectric unit 640 mayalso extend to a side portion 627 of the first electrode 620 as shown bybroken lines in FIG. 6A, or the first electrode 620 may completelycontain the thermoelectric unit 640. In some embodiments, thethermoelectric unit 640 may be integral with the first electrode 620.The configuration shown in FIG. 6A can protect the thermoelectric unitduring semiconductor processing. For example, the one or more processgases that enter the upper portion of the reactor may be corrosive oraggressive to the materials of the thermoelectric unit 640. Thus, thefirst electrode 620 can at least partially protect the embeddedthermoelectric unit 640 from potentially harmful process gases.

FIG. 6B is a schematic cross-sectional view of a first electrode andthermoelectric unit configuration in accordance with another embodimentof the invention. In this embodiment, a component 680 is both the firstelectrode and also the thermoelectric unit of the reactor. The component680 includes a front portion 688 having a front side 682, and a backportion 689 having backside 684. Accordingly, the front side 682 canemit heat while the backside 684 absorbs heat in a forward bias, or thefront side 682 can absorb heat while the backside emits heat in areverse bias. The component 680 can also include one or more channels oroutlets 686 similar to the outlets 226 described above. In thisconfiguration, the component 680 can operate similar to the combinationof the first electrode and the thermoelectric unit as described above toprovide accurate and consistent thermal control of the electrode.

FIG. 7A is a flow diagram of an embodiment of a method 700 forprocessing a semiconductor wafer with capacitively coupled plasma. Inthis embodiment, the method 700 includes positioning a semiconductorwafer in a processing chamber (block 705) and heating a first electrodewith a thermoelectric unit (block 710). The thermoelectric unit can be aPeltier unit, and heating the first electrode can include applying afirst voltage having a first polarity to the thermoelectric unit suchthat a first side of the thermoelectric unit proximate to the firstelectrode heats the first electrode while a second side of thethermoelectric unit opposite the first side absorbs heat. Thethermoelectric unit can also include a plurality of thermoelectricelements that are selectively and independently operable. The process700 can also include cooling the second side of the thermoelectric unitwhile the first side of the thermoelectric unit is heating the firstelectrode. The process 700 further includes distributing one or moregases in the processing chamber (block 720), and producing a plasma byapplying an energy to the one or more gasses between the first electrodeand a second electrode (block 730). The process 700 also includescooling and/or heating the first electrode with the thermoelectric unitwhile producing the plasma (block 740). The process of cooling the firstelectrode can include applying a second voltage having a second polarityopposite from the first polarity to the thermoelectric unit such thatthe first side of the thermoelectric unit proximate to the firstelectrode cools the first electrode. The process 700 can also includeheating the second side of the thermoelectric unit while the first sideof the thermoelectric unit is cooling the first electrode. In certainembodiments cooling and heating the first electrode can also includemonitoring a temperature of the first electrode or regions of the firstelectrode and operating the thermoelectric unit or thermoelectricelements based on the monitored temperature.

FIG. 7B is a flow diagram of an embodiment of a method 760 for heatingand cooling a first electrode in a capacitively coupled plasma reactor.The process 760 can include applying a first voltage at a first polarityto a thermoelectric unit positioned proximate to the first electrode toheat or cool the first electrode (block 770) during a first portion of acycle. The thermoelectric unit can be a Peltier unit, and thethermoelectric unit can heat the first electrode by conduction. Theprocess 760 also includes applying a second voltage to thethermoelectric unit (block 780). The second voltage has a secondpolarity opposite the first polarity and is applied to thethermoelectric unit during a second portion of the cycle to the other ofheating or cooling. The process 760 can further include heating and/orcooling a back surface of the thermoelectric unit while thethermoelectric unit heats or cools the first electrode.

From the foregoing it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thescope of the invention. For example, the elements of one embodiment canbe combined with other embodiments in addition to or in lieu of theelements of other embodiments. Accordingly, the invention is not limitedexcept by the appended claims.

I claim:
 1. A method of processing a semiconductor wafer with acapacitively coupled plasma in a reactor, the method comprising: heatinga first electrode disposed in an upper portion of the reactor to apredetermined temperature with a thermoelectric unit having a first sideopposite a second side, wherein the first side of the thermoelectricunit is in direct contact with a backside of the first electrode, andwherein the second side of the thermoelectric unit is exposed to theupper portion of the reactor, and; producing a plasma in a processingregion between the first electrode and a second electrode positioned atleast proximate the wafer, and cooling the first electrode with thefirst side of the thermoelectric unit while producing the plasma,wherein the thermoelectric unit is configured to selectively heat andcool the first electrode via the first side to maintain a generallyconstant temperature of the first electrode; wherein the second side ofthe thermoelectric unit is configured to heat the upper portion of thereactor when the first side of the thermoelectric unit cools the firstelectrode; and wherein the second side of the thermoelectric unit isconfigured to cool the upper portion of the reactor when the first sideof the thermoelectric unit heats the first electrode.
 2. The method ofclaim 1 wherein: heating the first electrode comprises providing avoltage having a first polarity to the thermoelectric unit such that thefirst side of the thermoelectric unit heats the first electrode; andcooling the first electrode comprises providing a voltage having asecond polarity opposite the first polarity to the thermoelectric unitsuch that the first side of the thermoelectric unit cools the firstelectrode.
 3. The method of claim 1 wherein the thermoelectric unitheats and cools the first electrode by conduction.
 4. The method ofclaim 1 wherein cooling and heating the second side of thethermoelectric unit comprises positioning a thermally controlled plateat least proximate the second side of the thermoelectric unit.
 5. Themethod of claim 4, further comprising regulating a temperature of thethermally controlled plate by flowing water through the thermallycontrolled plate.
 6. The method of claim 1, further comprising:monitoring a temperature of the first electrode; and activating thethermoelectric unit based on the temperature of the first electrode. 7.The method of claim 1 wherein the thermoelectric unit comprises at leasttwo thermoelectric elements configured to heat or cool different regionsof the first electrode.
 8. The method of claim 7, further comprising:monitoring one or more temperatures of the different regions of thefirst electrode; and activating at least one of the thermoelectricelements based on the temperature of the region of the correspondingthermoelectric element.
 9. A method of processing a microfeatureworkpiece with a capacitively coupled plasma in a reactor, the methodcomprising: heating a first electrode with a thermoelectric unit,wherein the first electrode and the thermoelectric unit are disposed inan upper portion of the reactor in fluid communication with a lowerportion of the reactor, wherein the first electrode includes a frontside opposite a back side, wherein the thermoelectric unit has a firstsurface opposite a second surface; wherein the first surface is exposedto the upper portion of the reactor; and wherein the second surface ispositioned in direct contact with the backside of the first electrode;producing a plasma in the reactor between the first electrode and asecond electrode in the lower portion; and maintaining a desiredtemperature of the first electrode during the plasma production bycooling and heating the first electrode with the thermoelectric unit atdifferent times, wherein the first surface of the thermoelectric unit isconfigured to heat the upper portion when the second surface of thethermoelectric unit cools the backside of the first electrode; andwherein the first surface of the thermoelectric unit is configured tocool the upper portion when the second surface of the thermoelectricunit heats the backside of the first electrode.
 10. The method of claim9 wherein: heating the first electrode with the thermoelectric unitcomprises applying a first voltage having a first polarity to thethermoelectric unit; and cooling the first electrode with thethermoelectric unit comprises applying a second voltage having a secondpolarity opposite from the first polarity to the thermoelectric unit.11. The method of claim 9 wherein the thermoelectric unit comprises atleast two thermoelectric elements.
 12. The method of claim 11, furthercomprising: monitoring a temperature of different regions of the firstelectrode; and operating one or more of the at least two thermoelectricelements according to the temperatures of the different regions.
 13. Amethod of processing a semiconductor wafer with a capacitively couplingplasma in a reactor, the method comprising: applying a first voltage ata first polarity to a thermoelectric unit, wherein the thermoelectricunit has a first surface opposite a second surface positioned proximatea backside of a first electrode in an upper portion of the reactor, andwherein at the first polarity, the second surface of the thermoelectricunit is configured to heat the first electrode and the first surface isconfigured to cool the upper portion of the reactor; producing a plasmain the reactor between the first electrode and a second electrodepositioned at least proximate the wafer; and maintaining a desiredtemperature of the first electrode during the plasma production byapplying a second voltage at a second polarity opposite the firstpolarity to the thermoelectric unit, wherein at the second polarity, thesecond surface is configured to cool the first electrode and the firstsurface is configured to heat the upper portion of the reactor.
 14. Themethod of claim 13 wherein the thermoelectric unit comprises a Peltierunit.
 15. The method of claim 13 wherein the second surface of thethermoelectric unit contacts the backside of the first electrode. 16.The method of claim 15 wherein the thermoelectric unit heats and coolsthe first electrode by conduction.
 17. The method of claim 13, furthercomprising heating and cooling the thermoelectric unit with atemperature controlled plate positioned at least proximate the firstsurface.
 18. The method of claim 17 wherein heating and cooling thethermoelectric unit with the temperature controlled plate comprisesflowing water through the temperature controlled plate.
 19. The methodof claim 18, further comprising flowing water at a generally constanttemperature.
 20. The method of claim 19 wherein the generally constanttemperature comprises room temperature.
 21. The method of claim 13,further comprising monitoring a temperature of the first electrode andselectively operating the thermoelectric unit based on the temperatureof the first electrode.
 22. The method of claim 13 wherein thethermoelectric unit comprises at least two thermoelectric elementscorresponding to different regions of the first electrode.
 23. Themethod of claim 22, further comprising monitoring a temperature of thedifferent regions of the first electrode and selectively operating thethermoelectric elements based on the temperature of the differentregions of the first electrode.
 24. A method of processing asemiconductor workpiece in a reactor, the method comprising: operating athermoelectric unit disposed in an upper portion of the reactor at afirst voltage, the thermoelectric unit having a first surface opposite asecond surface in thermal communication with a first electrode disposedin the upper portion of the reactor, wherein operating thethermoelectric unit at the first voltage includes— heating the firstelectrode by direct conduction via the second surface of thethermoelectric unit; and absorbing heat from the upper portion of thereactor via the first surface of the thermoelectric unit; ionizing oneor more process gases distributed in a processing chamber between thefirst electrode and a second electrode disposed at least proximate theworkpiece in the processing chamber; monitoring a temperature of thefirst electrode during the process gas ionization; and operating thethermoelectric unit at a second voltage when the temperature of thefirst electrode exceeds a predetermined desired temperature, whereinoperating the thermoelectric unit at the second voltage includes—absorbing heat from the first electrode by direct conduction via thesecond surface of the thermoelectric unit; and emitting heat from thefirst surface of the thermoelectric unit into the upper portion of thereactor.
 25. The method of claim 24, further comprising operating thethermoelectric unit at the first voltage when the temperature is lessthan the desired temperature.
 26. The method of claim 24, furthercomprising maintaining the desired temperature of the first electrodeduring process gas ionization by selectively operating thethermoelectric unit at the first and second voltages.
 27. The method ofclaim 24 wherein: operating the thermoelectric unit at the first voltagecomprises applying the first voltage to the thermoelectric unit with afirst polarity; and operating the thermoelectric unit at the secondvoltage comprises applying the second voltage to the thermoelectric unitwith a second polarity opposite the first polarity.
 28. The method ofclaim 24, further comprising flowing a cooling or heating medium througha thermal control unit disposed in the upper portion of the reactor andspaced apart from the first surface of the thermoelectric unit.